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2002 gmc envoy_slt
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547 Posts
Discussion Starter · #1 ·
I have checked R134 charge level. Perfect. Replaced low pressure/cycling switch. Exchanged relay (#44) with one from my headlight washer that I know works perfectly. The thing will work fine when I start out. Get's plenty cold. Then 10-15 minutes in, the compressor just shuts off. I've visually confirmed the compressor is off during these failures. Sometimes it will get cold again for a while then shut down again. The fan works perfectly. All the mix doors are working correctly. The GM shop mentioned something about the temp sensors on the mix doors going bad and shutting down the compressor. They haven't looked at it yet but said anywhere from $300-$700 to fix is these sensors are bad as they have to pull the whole dash apart.

I've also read something here about a TSB concerning reflashing the module for poor AC performance. Anyways, have anyone else had this problem? If so, what did it take to fix it? Thanks, c good (2002 SLT Envoy, I-6, 4X4)
 

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2002 gmc envoy_slt
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Discussion Starter · #3 ·
Haven't checked it yet. I haven't heard any whistle sound when accelerating, but to be honest havent' been listening for it either so will check that tomorrow. If it is HP switch do they go bad or is it possibly a clogged emulsion tube or something? Thanks for the input. c good
 

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2002 olds bravada
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2,369 Posts
I believe the SLT comes with the Dual Automatic Climate Control? If yes, make sure the temperature reading is correct.
 

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2004 gmc
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26,181 Posts
It has the digital, since the manual control one has no sensors on the mix doors. Yes, make sure the outside air temp sensor isn't telling you it's -50 degrees - that shuts off the compressor.

It might take a dealer's visit to diagnose for sure, since a lot of vehicle things can shut off the compressor from a PCM input, like thinking it's in WOT mode, or the PCM detecst excessive torque load or insufficient "idle quality". You have to catch it in the act, then ask it "why"?

The reflash came along in 2005, to address an issue with poor performance at idle after startup before the engine coolant was hot enough to call for higher fan clutch RPM. That's a good ting to have anyway unless they're going to rip you for ten minutes work with the tech tool.

The 2005 redesigned fan clutch will be good to put in WHEN your 2002 fan clutch dies, but we can talk you through that when it happens. It doesn't cause compressor shut offs.
 

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2002 gmc envoy_slt
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547 Posts
Discussion Starter · #7 ·
Updated. Pretty sure it's solved.

Hi All:
Just an update on this. After confirming sufficient R134 Charge, and replacing low pressure/cycling switch the Envoy was still having intermittent AC performance as described previously.

Finally got it to the dealer. They confirmed correct 134 levels, no compressor codes, ie overpressure, thermal cutout, etc. They downloaded the new software that addressed this problem and was supposed to be installed after 2003. Put 100 miles on it today with perfect AC! They also reflashed the BCM for the wandering side view mirrors and they're perfect now too! Starting to like this Envoy. c good
 

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2003 gmc envoy_slt
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8 Posts
Intermittent A/C

I took my car in and had them fully charge the system - they did a die test and checked for leaks - had a/c for about 10 minutes and then it fades away. I just replaced the compressor cycle switch and changed my hi beam relay to my a/c relay - no improvement - the a/c works fine in the morning and once it gets warm out - it quits working.

I just purchased a new PCM/ECM that will be reflashed with all the dealer updates and I hope this fixes the problems.

This whole thing is getting expensive - but A/C in Florida is a MUST.

:bonk:
 

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2002 gmc envoy_slt
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Discussion Starter · #11 ·
Bad AC clutch coil. It would get hot and loose magnetic strength. I ended up having to put in a new compressor. Others with similar problems have been able to remove a shim and tighten up the "air gap" on the clutch assembly. My coils would get weak when it heated up and not engage the compressor. HTH c good
 
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